Guard system

ABSTRACT

Rigid closed cell energy dissipaters for use in high-speed cutting tools interposed between the cutting tool and the inner surface of the cutting tool guard and/or the machine base and the cutting tool guard, for substantially dissipating the energy of impact of broken tool fragments. In addition, the cutting tool guard is capable of limited rotational movement and may be shearmounted.

United States Patent [72] Inventors IrvingJ.Stewart [54] GUARD SYSTEM 12 Claims, 8 Drawing Figs.

Primary Examiner-Granvilley Custer, Jr. Attorneys-.l-loward T. Keiser and Ernst H. Ruf

ABSTRACT: Rigid closed cell energy dissipaters for use in high-speed cutting tools interposed between the cutting tool [52] U.S.Cl. and the inner surface of the cutting tool guard and/or the 143/159 machine base and the cutting tool guard, for substantially dis- [51] Int. Cl. 1324b 55/04 sipating the energy of impact of broken tool fragments. In ad- [50] Field of Search 51/268, dition, the cutting tool guard is capable of limited rotational 269; 143/159; 144/251 movement and may be shear-mounted.

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J?.Z\ .L1 '1" /Q. I 1 4 PATENTED' MR2 3 I971 SHEET 1 BF 4 INVENTORS IRVING J STEWART LLOYD W. NELSON ATTORNEYS LPATENTEDAHARNIQYI sum 2 BF 4- PAIENTED m2 319?! SHEET U UF 4 GUARD SYSTEM BACKGROUND OF THE INVENTION This invention relates to high-speed cutting tool guards, especially guards for high-speed grinding wheels.

With the advent of high-speed grinding the energy of the grinding wheel, or any given fragment thereof, is much higher at high speed, more exactly, it is 3.41 times as high at 12,000 f.p.m. (feet per minute) as at the conventional speed of 6,500 f.p.m. This, of course, implies greater danger to operating personnel, and personnel safety during wheel blowup can only be assured by adequate control of the wheel fragments.

During the blowup of a grinding wheel, large amounts of energy are very rapidly transferred to the grinding machine wheelhead via the grinding wheel guard. Some means of absorbing this energy is necessary to protect both the operating personnel and the machine components. The critical requirement is that the dynamic force be reduced. During high-speed grinding the kinetic energy of a grinding wheel, rotating for example at 12,000 f.p.m., can reach or even exceed 200,000 foot pounds, which energy a grinding machine must somehow absorb in the event of a grinding wheel failure if it is to operate in a safe manner. The bolts currently used to fasten the grinding wheel guard to the wheelhead cannot safely absorb the higher energy levels imposed by the 12,000 f.p.m. wheel s eed.

In order to reduce the dynamic force, Newtons second law requires that the time during which energy is transmitted must be increased; i.e., the acceleration of the grinding wheel guard caused by impact of the broken wheel fragments must be reduced. The only way to stretch time is to insert a flexible link in the chain of parts that transmit energy.

Over the years various forms of energy dissipaters, such as crushable tubes or flexible spring liners and flexible liners of wood, cork, felt etc., have been suggested for interposing between the grinding wheel and the inner surface of the grinding wheel guard. Although these dissipaters are technically feasible, they may not be commercially practical, since solid deformable dissipaters, such as crushable tubes or flexible springlike liners, while helping to absorb some of the energy of impact of the broken wheel fragments do not aid in the retention of wheel fragments within the grinding wheel guard. Flexible liners such as wood, cork or felt etc., while both helping to absorb some wheel fragment energy and aiding in the retention of wheel fragments, suffer from the serious disadvantage that they are all of an open cellular construction which readily absorbs coolant and swarf. At the high-impact speeds of the wheel fragments these water or coolant-logged liners are somewhat incompressible and tend to transmit rather than absorb energy, and possible even more important, the retained moisture will cause a breakdown of the liner materials in addition to creating health and odor problems.

In order to nullify the lift imparted to the wheelhead by the impact of the grinding wheel fragments upon the inner surface of the grinding wheel guard it is known in the art to interpose solid defonnable dissipaters such as crushable tubes or rigid skeletallike structures, between guides on the wheel slide and the ways on the machine base. While this may be helpful, the area available for interposing this dissipator is quite small and the dissipator is quite rigid thus providing very nonuniform deceleration. In addition, this design is a somewhat after-thefact solution since, if enough energy is transmitted from the wheel guard to the wheelhead to cause lifting of the wheelhead, then already, at least some damage to the machine components hasalready occurred before the interposed dlssipator becomes operative, and most likely the wheel guard has already broken loose from its mounting on the wheelhead.

SUMMARY or THE INVENTION This invention solves the previously mentioned problems by interposing expendable energy dissipaters between the grinding wheel fragments and the inner peripheral surface of the grinding wheel guard, with these dissipaters being of a rigid closed cell construction, preferably of an energy absorbing plastic, for example polyurethane foam. These dissipaters may be removably fastened to-the inside of the grinding wheel guard so that when damaged they may be readily replaced. The expendable energy dissipaters of this invention not only absorb a large fraction of the energy of impact of the broken wheel fragment but also help in retaining and restraining a substantial number of wheel fragments within the grinding wheel guard. In addition, the closed cell construction avoids both moisture absorption and breakdown of the linear material.

Since all of the energy of impact cannot readily be absorbed at this link in the chain a further energy absorber or dissipator is inserted between the grinding wheel guard and the machine base. While this second energy dissipator, or compression pad, may be constructed of any crushable or deformable material, it is preferably of rigid closed cell construction. Unlike the prior art constructions, this dissipator is coupled between the grinding wheel guard and the machine base, not between the wheelhead and the base, so that very little of the impact energy of the wheel fragments is actually transmitted to the wheelhead itself. In addition, use of the closed cell construction provides much more uniform deceleration and avoids dissipator deterioration and health problems.

In order to permit the maximum stretching of time" the mounting of the grinding wheel guard is so designed so as to allow limited rotational movement of the grinding wheel guard with respect to the centerline of the grinding wheel spindle upon the impact of wheel fragments within the grinding wheel guard. In addition, mounting bolts which acts as shear bolts may be utilized to help dissipate a fraction of the energy of the impact. Almost immediately upon the start of rotation of the grinding wheel guard the second energy absorber inserted between the grinding wheel guard and the machine base is progressively permanently deformed as guard rotation continues.

In summary, this invention provides expendable energy dissipaters for a high-speed cutting tool, for example a grinding machine having a base with ways and a wheelhead thereon for mounting a rotatable grinding wheel and a pivotable grinding wheel guard. These expendable energy dissipaters include a first rigid closed cell deformable means slidably secured to the inside surface of the grinding wheel guard for both dissipating, by a permanent deformation of this rigid closed cell deformable means, at least part of the energy released by grinding wheel breakage, and for retaining and restraining a substantial number of wheel fragments within the wheel guard; and a second rigid closed cell deformable means interposed between the machine base and the grinding wheel guard for dissipating by permanent deformation of this second rigid closed cell deformable means at least part of the energy released by grinding wheel breakage, with the impact of said grinding wheel fragments causing limited pivoting of the grinding wheel guard. Furthermore, mounting bolts acting as shear bolts may be used in the grinding wheel mounting to help dissipate a fraction of the energy of the impact of the grinding wheel fragments.

BRIEF DRAWING DESCRIPTION FIG. 1 isan end view of a grinding machine embodying the elements of this invention.

FIG. 2 is an enlarged front view looking in the direction of arrow 2 of FIG. 1.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2.

FIG. 4 is a sectional view taken along line 4-4 of FIG. 2.

FIGS. 5 and 6 are fragmentary sectional views taken along lines 5-5 and 66 respectively, of FIG. 3.

FIG. 7 is a composite sectional view similar to the upper half of FIG. 3 and the lower half of FIG. 4 but showing the elements of this invention in a different condition.

FIG. 8 illustrates a modified form of this invention.

DETAILED DESCRIPTION Referring now to the drawings in detail, FIGS. 1 and 2 depict grinding machine 10 having support or base 12 with way portion 14 for slidably receiving wheelhead 16. wheelhead or cutting tool slide 16 has mounted in it on suitable bearings (not shown), a grinding spindle 18 to one end of which is fixedly attached a grinding or cutting wheel 20 and the other end of which (not shown) is suitably connected, in any of the ways well-known in the art, to drive motor 22, for rotating grinding wheel 20. Since this invention is illustrated on a center type grinding machine although it is applicable to all types of highspeed cutting tools or grinders, it also includes a table portion 23 attached to or forming part of base 12 and further includes a slide 24 carrying a power-driven headstock (not shown) and a footstock 26 for rotatably carrying workpiece 28 therebetween.

Rigidly attached to base 12 and partially involving grinding wheel 20 is stationary operator-protective shield 30 which is thoroughly described in copending US. application Ser. No. 822,l l9 filed May 6, 1969 and also assigned to the assignee of this invention. Rigidly but movably attached to wheelhead l6 and partially enveloping a complementary part of grinding wheel 20 is grinding wheel guard 32. Operator-protective shield 30 and grinding wheel guard 32 are designed to be at all times in overlapping telescoping relationship with regard to each other in the operating positions of cutting tool slide 16. The general construction of grinding wheel guard 32 of this invention, which is preferably constructed of sheet or plate steel, can best be seen by reference to FIGS. 1 to 4 which show it to be comprised of three main portions: namely stepped plate 34 (FIGS. 2 and 4) peripheral surface plate 54 (FIGS. 3) and side cover plate 76 (FIGS. 1 and 2).

Stepped plate 34 (FIG. 4), which has integral lower stepped portion 36 with flange 38, is attached on its upper portion 40 to wheelhead 16 by mounting bolts 42 in holes 44 and multiples of bolts 46, having washers 48, extending through enlarged holes or slots 50. See FIGS. 5 and 6 for detailed views of this mounting.

Fixedly secured, such as by welding, to stepped plate 34 is peripheral surface plate 54 (FIG. 3) having upper portion 56 and lower portion 58, with both portions having pluralities of spaced integral bosses 60 with threaded holes 62 spaced along inner peripheral surface 64. Upper portion 56 has vertically depending flange 57 and lower portion 58 has horizontally extending flange 59, both flanges extending from the upper ends of portions 56, 58 respectively. Peripheral surface plate 54 also has a rear opening 66 between the lower end of upper portion 56 and flange 59 of lower portion 58, with adapter plate 68, having central opening 70, partially fitting therebetween and being secured to plate 54 by means of multiples of bolts 71 and 72. The primary function of adapter plate 68 is to provide a suitable opening 70 to allow for the ingress and egress of a grinding wheel dressing tool (not shown) of conventional construction.

Fixedly attached to peripheral surface plate 54 by means of multiples of bolts 78 extending through holes 80, corresponding in location to threaded hole 62 is generally C-shaped formed side cover plate 76. In addition, bolts 81 extending through holes 82 are used to secure cover plate 76 to adapter plate 68.

As best seen in FIG. 3 disposed between grinding wheel 20 and upper and lower portions 56 and 58 or peripheral surface plate 54 are upper and lower expendable energy dissipaters or rigid closed cell deformable means 84 and 86, having their outer surfaces 88 and 90 respectively, shaped to complement and abut their respective portions of inner peripheral surface 64 of plate 54, while their inner peripheral surfaces 92 and 94 respectively are shaped in similar correspondency or conformity with the periphery of grinding wheel 20 but slightly displaced therefrom. Ends 96 and 98 of dissipaters 84 and 86 abut flanges 57 and 59 of peripheral surface plate portions 56 and 58 respectively, while ends 102 and 104 are free of abutments. Dissipaters 84 and 86 are slidingly secured on studs 106, 108 respectively, with studs 106, 108 being affixed to stepped plate 34.

As best seen in FIGS. 2 and 4, fixedly attached to base 12 parallel with way portion 14, by multiples of bolts I14 and holes 112 is stationary stop member 110. Interposed between stop member and stepped plate flange 38 is energy dissipator or rigid closed cell deformable means 116. While not touching stop member 110 with its upper surface 118, dissipator 116 is attached on its lower surface 120 to flange 38 by bolts 121. Rear surface 122 of dissipator 116 abuts stepped plate lower portion 36 while front surface 124 closely approaches, but does not touch, base 12. Ends 126, 128 are free of abutments. During the'normal traversing of wheel slide 16 on ways 14 dissipator 116 never comes into actual contact with stop member 110.

During normal machine operation all elements are in the condition and position shown in FIGS. 1 to 6. Breakage of a cutting tool or grinding wheel most often generally starts along a single axial line at the wheel bore and propagates rapidly outward to its outside diameter. The outside diameter of the grinding wheel rotates only a fraction of an inch during this short time, so that the cracking can be considered substantially instantaneous. The tangential bore stress is relieved near the crack, but it is generally increased away as the crack starts to open, therefore, the next crack fonns one-fourth to one-half way around the grinding wheel ahead of the initial crack, unless grinding is going on in this zone. In any case, except for some crumbling that occurs when the cracks meet the outside diameter, only a limited number of large primary fragments will be formed (primary fragments, may be defined as those that have not yet directly impacted upon the grinding wheel guard). FIG. 7, which is a composite sectional view similar to the upper half of FIG. 3 and the lower half of FIG. 4, shows grinding wheel 20 broken up into multiple fragments 21, and grinding wheel guard 32 rotated from its original position shown in FIG. 3.

In accordance with this invention expendable energy dissipaters 84 and 86 are interposed between wheel fragments 21 and inner peripheral surface 64 of grinding wheel guard 32. These dissipaters preferably are of rigid closed cell construction, i.e. composite structures having solid walls and containing a gas, such as energy absorbing plastic foam, for example polyurethane foam. Dissipaters 84 and 86 are easily replaceable by being slidably secured within peripheral surface plate 54 by studs 106, 108 respectively and have their outer surfaces 88 and 90 respectively abutting their respective portion of inner peripheral guard surface 64.

Extensive tests by the inventors have shown that a large fraction of the energy of impact of broken wheel fragments 21 is absorbed by dissipaters 84 and 86 by permanent deformation thereof. In addition thereto, dissipaters 84 and 86 also help in retaining and restraining a substantial number of wheel fragments 21 within grinding wheel guard 32. Furthermore, the closed cellular construction positively prevents both moisture and swarf absorption which tend to reduce the desired deformation, cause liner deterioration and cause health problems. The upper half of FIG. 7 illustrates both the retention of wheel fragments 21 and the deformation of dissipator 84.

Since all of the energy of impact cannot be readily absorbed at this link in the chain a further energy absorber or dissipator is inserted between the grinding wheel guard or hood and the machine base. Further in accordance with this invention expendable energy dissipator I16 is interposed between flange 38 of grinding wheel guard 32 and stop member 110 on machine base 12. Dissipator 116, which is easily replaceable, is attached to flange 38 by bolts 12]. While energy dissipator or compression pad 116 may be constructed of any deformable material it is preferably of rigid closed cell construction, such as energy absorbing plastic, for example polyurethane foam. Again, this construction avoids the absorber deterioration and health problems as well as allowing substantially uniform deceleration.

As best seen in FIGS. 4 to 6 wheel guard 32 is attached to wheelhead 16 by mounting bolts 42 and bolts 46, having washers 48, extending through enlarged holes 50. This mounting is designed to allow controlled limited rotational or pivotal movement of grinding wheel guard 32 with respect to the centerline of grinding spindle 18 upon the impact of wheel fragments 21upon grinding wheel guard 32, as shown in FIG. 7. Upon impact of fragments 21 mounting bolts 42 are sheared, this shearing action helping to dissipate a fraction of the energy of impact, and guard 32 starts to rotate to the extend allowed by enlarged holes 50, with the frictional force between washers 48 and upper portion 40 of step plate 34 also helping to dissipate a small fraction of the energy of impact.

In addition to the above, almost immediately upon the start of rotation of grinding wheel guard 32 dissipator 116 comes into contact with stop member 110 and is progressively perthanently deformed as rotation continues, with this defonnation absorbing at least part of the energy of impact of grinding wheel fragments 21 upon guard 32.

In the modified form of this invention shown in FIG. 8, which is a sectional view similar to that of FIG. 3, like numerals are used on all parts similar to those shown in FIGS. 1 to 7. For the sake of clarity, and since fully described in FIGS.

1 to 7, most fasteners have been deleted from FIG. 8.

Again, grinding wheel guard 132 is comprised of three main portions; namely, attachment plate 134, peripheral surface plate and side cover plate 162.

Attachment plate 134 is attached to wheelhead 16 by multiples of bolts 46, having washers 48, extending through enlarged holes or slots 50. Fixedly secured to attachment plate 134 is generally C-shaped peripheral surface plate 154 having depending integral rear boss portion 156 with flange portions 158, 159, which define an open T-slot. Fixedly but removably attached to peripheral surface plate 154 is side cover plate 162.

Interposed between plates 134 and 162 and touching the inner peripheral surface of plate 154 is expendable energy dissipator or rigid closed cell deformable means 166, for example polyurethane foam, having its inner peripheral surface 168 shaped in similar correspondency with the periphery of grinding wheel 20 but slightly displaced therefrom.

Slidably secured in the 'T-slot defined by flange portion 158, 159 is T-shaped head 176 of stationary deformable compression means or pad 170 also having foot portion 172, rod portion 174 and expendable energy dissipator 178. Preferably, energy dissipator or rigid closed cell defonnable means 178 is constructed of polyurethane foam.

Dissipator 178 is disposed between compression pad foot portion 172 and wall portion 13 of machine base 12, with compression pad rod portion 174 freely extending through opening in base portion 13. Thus, even though compression means 170 is stationary, it is at all times coupled with grinding wheel guard 132 regardless of the position of wheelhead 16 since flange portions 158, 159 are in sliding engagement with T-shaped head 176.

During normal operation all elements are in the condition and position shown in FIG. 8. Upon the blowup of grinding wheel expendable energy dissipator 166 performs in substantially the same manner as previously described dissipaters 84 and 86, while grinding wheel guard 132 is allowed to rotate to the extent allowed by enlarged holes or slots 50. Again, a small fraction of the energy of impact of grinding wheel fragments 21 is dissipated by the frictional force between washers 48 and attachment plate 134. Almost immediately upon the rotation of grinding wheel guard 132 dissipator 178, between foot portion 172 and machine base wall portion 13, is progressively crushed or deformedas rotation continues. Thus, the

energy of impact of wheel fragment 21 is substantially absorbed by the combination of dissipator 166, the rotation of grinding wheel guard 32 and dissipator 178.

Of course it should be evident from the preceding description that in both the embodiments of this invention shown in FIGS. 1-7 and FIG. 8 the following combinations may be utilized:

a. use of only first dissipaters 84, 86 (or 166) and grinding wheel guard 32 (or 132) nonrotatably affixed to wheelhead 16.

b. use of only first dissipaters 84, 86 (or 166) and grinding wheel guard 32 (or 132) rotatably affixed to wheelhead 16 and allowing limited rotational movement of the grinding wheel guard.

c. use of second dissipator 116 (or I78) and grinding wheel guard 32 (or 132) affixed to wheelhead 16 and allowing limited rotational movement of the grinding wheel guard.

d. use of first dissipaters 84, 86 (or 166) and 116 (or 178) and grinding wheel guard 32 (or 132) affixed to wheelhead 16 and allowing limited rotational movement of the grinding wheel guard.

For maximum protection to both the operating personnel and the machine; components combination (d) above is preferred.

While the use of this invention is of special significance with respect to high-speed grinding, it will also provide significantly increased operator protection even at conventional wheel speeds.

While this invention has been described in connection with possible forms or embodiment thereof, it is to be understood I that the present disclosure is illustrative rather than restrictive and that changes or modifications may be restored to without departing from the spirit of the invention.

We claim:

. 1. In a grinding machine:

a. a base;

b. a wheel slide mounting a grinding wheel and a hood therefor, with the hood, which encloses the grinding wheel, being capable of limited rotational movement with respect to the wheel slide and adapted to constrain wheel fragments upon breakage of the grinding wheel;

c. ways on the base supporting the wheel slide for translational movement relative to the work to be ground;

' d. a rigid closed cell deformable means juxtaposed with the inside surface of the hood for both dissipating at least part of the energy of the impact of the broken wheel fragments against the deformable means by permanent deformation thereof and for retaining and restraining a substantial number of the wheel fragments within the hood; and

e. a deformable compression pad disposed in the machine base operatively connected to the hood for absorbing, by permanent deformation thereof, at least part of the energy of the impact of the broken wheel fragments upon limited rotational movement of the hood.

2. In a grinding machine:

a. a base;

b. a wheelhead for mounting a grinding wheel and a guard thereon, with the guard, which encloses the grinding wheel, being capable of limited rotational movement with respect thereto and adapted to constrain wheel fragments upon breakage of the grinding wheel;

. ways on the base supporting the wheelhead for translational movement relative to the work to be ground;

d. a first rigid closed cell deformable means juxtaposed with the inside surface of the guard for both dissipating at least part of the energy of the impact of the broken wheel fragments against the deformable means by permanent deformation thereof and for retaining and restraining a substantial number of the wheel fragments within the guard; and

e. a second rigid closed cell deformable means interposed between the machine base andthe guard for absorbing at least part of the energy of the impact of the broken wheel fragments by permanent deformation thereof upon limited rotational movement of the guard.

3. In a grinding machine:

a. a base;

b. a wheelhead for rotatably mounting a grinding wheel and for fixedly but yieldingly mounting a grinding wheel guard, with the guard, which substantially encloses the grinding wheel to constrain wheel fragments released if the grinding wheel breaks, being capable of limited rotational movement with respect to said wheelhead for dissipating at least part of the energy of the impact;

c. ways on the base supporting the wheelhead for translational movement relative to the work to be ground;

d. a first rigid closed cell deformable means slidingly secured to the inside surface of the wheel guard for both dissipating at least part of the energy of the impact of the broken wheel fragments against the deformable means by permanent deformation thereof and for retaining and restraining a substantial number of the wheel fragments within the wheel guard; and

e. a second rigid closed cell deformable means interposed between the machine base and the wheel guard for absorbing at least part of the energy of the impact of the broken wheel fragments by permanent deformation thereof upon controlled limited rotational movement of the wheel guard.

4. ln a grinding machine:

a. a base;

b. a wheelhead for rotatably mounting a grinding wheel and for shear-mounting a grinding wheel guard, with said guard, which substantially encloses said grinding wheel to constrain wheel fragments if the grinding wheel breaks, being capable of limited rotational movement with respect to said wheelhead upon breakage of said grinding wheel, said limited rotational movement dissipating at least part of the energy of the impact of the broken wheel fragments;

c. ways on the base supporting the wheelhead for translational movement relative to the work;

d. a first rigid closed cell deformable means slidably secured to the inside surface of the wheel guard for both dissipating at least part of the energy of the impact of the broken wheel fragments against the deformable means by permanent deformation thereof and for retaining and restraining a substantial number of the wheel fragments within the wheel guard; and

e. a second rigid closed cell deformable means interposed between the machine base and the wheel guard for absorbing at least part of the energy of the impact of the broken wheel fragments by permanent deformation thereof upon limited rotational movement of the wheel guard.

. In a grinding machine:

a base;

. a wheelhead for rotatably mounting a grinding wheel and for pivotally mounting a grinding wheel guard, said wheel guard substantially enclosing said grinding wheel for constraining wheel fragments if said grinding wheel breaks;

c. ways on the base supporting the wheel slide for translational movement relative to the work;

d. rigid closed cell deformable means secured to the inside surface of the wheel guard;

e. a deformable compression pad disposed in the machine base and operatively connected to the wheel guard whereby the pivoting of the wheel guard in conjunction with said deformable compression pad and said rigid closed cell deformable means substantially dissipates the energy of the impact of the broken wheel fragments and said rigid closed cell deformable means retains and restrains a substantial number of the wheel fragments within said wheel guard.

6. An expendable energy dissipator for grinding-wheel-type gfiinding machines comprising closed cell deformable means s aped o be disposed between and secured to one of opposed spaced relatively more rigid but movable elements of the grinding machine without restricting the relative movement of the spaced grinding machine elements under normal operating conditions, so that relative movement of one grinding machine element in the event of grinding wheel failure is cushioned by permanent deformation of said closed cell deformable means.

7. An expendable energy dissipator for a grinding machine having a base with ways and a movable wheelhead thereon for mounting a rotatable grinding wheel and a pivotable grinding wheel guard comprising rigid closed cell deformable means interposed between the machine base and the wheel guard for dissipating by pennanent deformation of said rigid closed cell deformable means at least part of the energy released by grinding wheel breakage which causes limited pivoting of said wheel guard.

8. An expendable energy dissipator for a grinding machine having a base with ways and a wheelhead thereon for mounting a rotatable grinding wheel and a grinding wheel guard comprising rigid closed cell deformable means slidably secured to the inside surface of the wheel guard for both dissipating by permanent deformation of said rigid closed cell deformable means at least part of the energy released by grinding wheel breakage and for retaining and restraining a substantial number of wheel fragments within the wheel guard.

9. Expendable energy dissipaters for a grinding machine having a base with ways and a wheelhead thereon for mounting a rotatable grinding wheel and a pivotable grinding wheel guard comprising:

a. first rigid closed cell deformable means slidably secured to the inside surface of the wheel guard for both dissipating by permanent deformation of said rigid closed cell deformable means at least part of the energy released by grinding wheel breakage and'for retaining and restraining a substantial number of wheel fragments within the wheel guard; and 4 b. second rigid closed cell deformable means interposed between the machine base and the wheel guard for dissipating by permanent deformation of said second rigid closed cell deformable means at least part of the energy released by grinding wheel breakage which causes limited pivoting of said wheel guard.

10. The expendable energy dissipator of claim 9 wherein said first and second rigid closed cell deformable means are energy absorbing plastic.

11. The expendable energy dissipator of claim 9 wherein said first and second rigid closed cell deformable means are polyurethane foam.

12. The expendable energy dissipator of claim 9 wherein said first and second rigid closed cell deformable means are composite structures having solid walls containing a gas. 

1. In a grinding machine: a. a base; b. a wheel slide mounting a grinding wheel and a hood therefor, with the hood, which encloses the grinding wheel, being capable of limited rotational movement with respect to the wheel slide and adapted to constrain wheel fragments upon breakage of the grinding wheel; c. ways on the base supporting the wheel slide for translational movement relative to the work to be ground; d. a rigid closed cell deformable means juxtaposed with the inside surface of the hood for both dissipating at least part of the energy of the impact of the broken wheel fragments against the deformable means by permanent deformation thereof and for retaining and restraining a substantial number of the wheel fragments within the hood; and e. a deformable compression pad disposed in the machine base operatively connected to the hood for absorbing, by permanent deformation thereof, at least part of the energy of the impact of the broken wheel fragments upon limited rotational movement of the hood.
 2. In a grinding machine: a. a base; b. a wheelhead for mounting a grinding wheel and a guard thereon, with the guard, which encloses the grinding wheel, being capable of limited rotational movement with respect thereto and adapted to constrain wheel fragments upon breakage of the grinding wheel; c. ways on the base supporting the wheelhead for translational movement relative to the work to be ground; d. a first rigid closed cell deformable means juxtaposed with the inside surface of the guard for both dissipating at least part of the energy of the impact of the broken wheel fragments against the deformable means by permanent deformation thereof and for retaining and restraining a substantial number of the wheel fragments within the guard; and e. a second rigid closed cell deformable means interposed between the machine base and the guard for absorbing at least part of the energy of the impact of the broken wheel fragments by permanent deformation thereof upon limited rotational movement of the guard.
 3. In a grinding machine: a. a base; b. a wheelhead for rotatably mounting a grinding wheel and for fixedly but yieldingly mounting a grinding wheel guard, with the guard, which substantially encloses the grinding wheel to constrain wheel fragments released if the grinding wheel breaks, being capable of limited rotational movement with respect to said wheelhead for dissipating at least part of the energy of the impact; c. ways on the base supporting the wheelhead for translational movement relative to the work to be ground; d. a first rigid closed cell deformable means slidingly secured to the inside surface of the wheel guard for both dissipating at least part of the energy of the impact of the broken wheel fragments against the deformable means by permanent deformation thereof and for retaining and restraining a substantial number of the wheel fragments within the wheel guard; and e. a second rigid closed cell deformable means interposed between the machine base and the wheel guard for absorbing at least part of the energy of the impact of the broken wheel fragments by permanent deformation thereof upon controlled limited rotational movement of the wheel guard.
 4. In a grinding machine: a. a base; b. a wheelhead for rotatably mounting a grinding wheel and for shear-mounting a grinding wheel guard, with said guard, which substantially encloses said grinding wheel to constrain wheel fragments if the grinding wheel breaks, being capable of limited rotational movement with respect to said wheelhead upon breakage of said grinding wheel, said limited rotational movement dissipating at least part of the energy of the impact of the broken wheel fragments; c. ways on the base supporting the wheelhead for translational movement relative to the work; d. a first rigid closed cell deformable means slidably secured to the inside surface of the wheel guard for both dissipating at least part of the energy of the impact of the broken wheel fragments against the deformable means by permanent deformation thereof and for retaining and restraining a substantial number of the wheel fragments within the wheel guard; and e. a second rigid closed cell deformable means interposed between the machine base and the wheel guard for absorbing at least part of the energy of the impact of the broken wheel fragments by permanent deformation thereof upon limited rotational movement of the wheel guard.
 5. In a grinding machine: a. a base; b. a wheelhead for rotatably mounting a grinding wheel and for pivotally mounting a grinding wheel guard, said wheel guard substantially enclosing said grinding wheel for constraining wheel fragments if said grinding wheel breaks; c. ways on the base supporting the wheel slide for translational movement relative to the work; d. rigid closed cell deformable means secured to the inside surface of the wheel guard; e. a deformable compression pad disposed in the machine base and operatively connected to the wheel guard whereby the pivoting of the wheel guard in conjunction with said deformable compression pad and said rigid closed cell deformable means substantially dissipates the energy of the impact of the broken wheel fragments and said rigid closed cell deformable means retains and restrains a substantial number of the wheel fragments within said wheel guard.
 6. An expendable energy dissipator for grinding-wheel-type grinding machines comprising closed cell deformable means shaped to be disposed between and secured to one of opposed spaced relatively more rigid but movable elements of the grinding machine without restricting the relative movement of the spaced grinding machine elements under normal operating conditions, so that relative movement of one grinding machine element in the event of grinding wheel failure is cushioned by permanent deformation of said closed cell deformable means.
 7. An expendable energy dissipator for a grinding machine having a base with ways and a movable wheelhead thereon for mounting a rotatable grinding wheel and a pivotable grinding wheel guard comprising rigid closed cell deformable means interposed between the machine base and the wheel guard for dissipating by permanent deformation of said rigid closed cell deformable means at least part of the energy released by grinding wheel breakage which causes limited pivoting of said wheel guard.
 8. An expendable energy dissipator for a grinding machine having a base with ways and a wheelhead thereon for mounting a rotatable grinding wheel and a grinding wheel guard comprising rigid closed cell deformable means slidably secured to the inside surface of the wheel guard for both dissipating by permanent deformation of said rigid closed cell deformable means at least part of the energy released by grinding wheel breakage and for retaining and restraining a substantial number of wheel fragments within the wheel guard.
 9. Expendable energy dissipaters for a grinding machine having a base with ways and a wheelhead thereon for mounting a rotatable grinding wheel and a pivotable grinding wheel guard comprising: a. first rigid closed cell deformable means slidably secured to the inside surface of the wheel guard for both dissipating by permanent deformation of said rigid closed cell deformable means at least part of the energy released by grinding wheel breakage and for retaining and restraining a substantial number of wheel fragments within the wheel guard; and b. second rigid closed cell deformable means interposed between the machine base and the wheel guard for dissipating by permanent deformation of said second rigid closed cell deformable means at least part of the energy released by grinding wheel breakage which causes limited pivoting of said wheel guard.
 10. The expendable energy dissipator of claim 9 wherein said first and second rigid closed cell deformable means are energy absorbing plastic.
 11. The expendable energy dissipator of claim 9 wherein said first and second rigid closed cell deformable means are polyurethane foam.
 12. The expendable energy dissipator of claim 9 wherein said first and second rigid closed cell deformable means are composite structures having solid walls containing a gas. 